1. Field of the Invention
The present invention relates to an improvement in a semiconductor strain measuring apparatus which is particularly adapted to produce electric output signals indicative of physical strains.
2. Description of the Prior Art
Semiconductor strain measuring instruments which comprise a single crystal silicon substrate including a strain sensitive region formed thereon and strain gauges formed integrally on the surface of the strain sensitive region are well known. Such a semiconductor strain measuring instrument is currently utilized in various applications because it can electrically detect any physical strain created in the strain sensitive region of the substrate through the strain gauges.
A strain measuring instrument including diffusion strain gauges is currently used in various fields such as automobile measurements, industrial measurements and medical measurements. The strain measuring instrument utilizing such diffusion strain gauges can easily be miniaturized using IC techniques and be superior in the mechanical characteristics. Accordingly, a strain measuring instrument of this type is being used to measure pressure at minute locations.
Thus, semiconductor strain measuring instruments are today utilized in various applications and will increasingly be applied to a wide range of applications. The semiconductor strain measuring instruments are particularly important in the automobile industry wherein precise measurement of pressure is required at various locations in an engine to control the engine with high precision and then to utilize fuel more efficiently. It is therefore expected to provide semiconductor strain measuring instruments which can determine pressures at locations in an engine.
However, the semiconductor strain measuring instruments of the prior art are subject to rapid degradation at high-temperatures and will be inoperative at temperatures above 180.degree. C.
It is therefore impossible to use the conventional semiconductor strain measuring instruments for measuring pressure at various parts in an engine which may be heated to raised temperatures, sometimes above 250.degree. C.